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Conch wreaking havoc on oyster beds

Invasive native crown conch destroying oyster, clam beds

Brandon Mellin, a Florida Master Naturalist and guide at Ripple Effect Kayaking and Eco Tours, lets a Florida Crown Conch move along his wrist while in the southern component of the Guana Tolomato Matanzas National Estuarine Research Reserve, near Marineland, on Thursday morning, December 1, 2011. BY DARON DEAN, daron.dean@staugustine.com

Brandon Mellin, a Florida Master Naturalist and guide at Ripple Effect Kayaking and Eco Tours, holds a Florida Crown Conch while in the southern component of the Guana Tolomato Matanzas National Estuarine Research Reserve, near Marineland, on Thursday morning, December 1, 2011. BY DARON DEAN, daron.dean@staugustine.com

Invasive native crown conch destroying oyster, clam beds

A Florida crown conch population explosion is decimating the oyster populations in Southern St. Johns County, scuttling the livelihoods of those who rely on the water for a living.

The conchs, which have spiral shells with brown or purple-brown streaks, eat oysters and clams, killing whole reefs, and hindering crabbers, who find their traps filled with the creatures.

Yet, it’s a mystery why the animals, native to the area, have multiplied enough to kill off entire oyster beds.

And Frankie Pacetti, a former commercial crabber whose husband, E.J. Pacetti, still crabs, said the conchs hurt their business.

“Certain times of the year, there are tons of them and they get in the traps and they destroy a lot of stuff,” Pacetti said. “They’re a problem. They get in a traps and they make it difficult to pull traps because of all those conchs.”

At least Brandon Mellin, a master naturalist and tour guide with Ripple Effect Ecotours, had something nice to say.

“They’re wreak-

ing havoc on oysters, but they’re great for tour guides,’ said Mellin, who spends his days on the waters of the Guana Tolomato Matanzas National Estuarine Research Reserve. “Because if you hold them, they’ll come out of their shell and walk around.”

And when you put them back in the water, they go back to eating oysters.

‘A freak show’

David Kimbro, assistant scholar scientist at the FSU marine lab, said data collected by one of his graduate students, Hanna Garland, show the mollusk burning through oyster beds, particularly those near Matanzas Inlet.

“This is really important to the local community because our monitoring reefs and the conch infested area used to be the most productive area in St. Augustine for harvesting oysters and rearing clams,” he wrote in an online blog. “But now, aquaculture leases here have been abandoned and a very large population of crown conchs appears to have taken up residence.”

He said Garland collected data to find out whether the animals ate oysters that were killed off by something else, or whether the conch caused the destruction.

It was the conchs, without a doubt, he said.

“Down in the southern part of Matanzas, it’s like a freak show how abundant they are,” Kimbro said.

But the real question now is: why?

“Something is just out of whack with the system,” Kimbro said. “That’s what we’re on to next.”

Cause murky

The conchs are the direct cause of the die-off, Kimbro said. “But what is ultimately causing this problem is whatever (would normally be) limiting the distribution of the crown conch.”

And that’s not known yet, he said.

The animal is native to Florida, “but their numbers are benign” elsewhere, he said.

Wendy Eash-Loucks, biological scientist with the Guana Tolomato Matanzas National Estuarine Research Reserve, said it’s hard to imagine a native species causing such destruction.

“I really don’t think they’re an issue,” she said. “I know for a long time people have blamed them but I haven’t seen any evidence.”

And to the north of the county, she’s right.

The conchs haven’t overtaken the oyster beds in Salt Run, one of just two public harvesting areas, said Carl Blow, former Port and Waterway commissioner.

“The reefs go from looking really bad to looking really good as you go from south to north,” he said. And they look the worst around Matanzas inlet, near where the Summer Haven River has become progressively clogged with sand.

“You could tell something was wrong with the system” there, Kimbro said.

He’s just not sure what.

He said it could be that there aren’t enough natural predators in the area, though he isn’t sure the creature, which has a very tough shell, had many to begin with.

“Very few things could break that shell, but we still have to look,” he said. It could also have to do with water temperature or salinity changes.

Blow said some suspect that the death of the Summer Haven River “greatly reduced the flushing action of the tide” and changed the salinity of the water there.

But that remains to be seen. Kimbro said he and Garland would probably need a year or two to figure out the root cause.

That leaves question marks on the horizon.

“Is this problem expanding? I don’t know.” Kimbro said.

About the conch:

The Florida crown conch is a large, predatory snail that can grow to 8 inches.

They live on both coasts of Florida, often found in seagrass beds, mangroves and oyster reefs in water up to 6 feet deep.

They range as far as Alabama in the Gulf of Mexico.

They’re carnivorous, eating mollusks and bivalves like oysters and clams. They also are scavengers, eating food that is already dead.

Source: Smithsonian Marine Station at Fort Pierce, Florida State University